We wish to determine the function of genes coded in the mouse H-2 complex in immune responses. We will examine the role of Ia ion promoter cells in the proliferative response to Con A and in the response to syngeneic tumors. We will map the Ia determinants expressed on various functional lymphocyte subsets including LPS responder, LPS specific suppressor cells, as well as T cells required for dependent humoral responses including macrophages. We will determine the expression of Ia antigens on macrophage and B cell clones, and chemically characterize Ia from epidermal cells and macrophages, and determine their biochemical relationship to lymphocyte Ia. We will further examine nonresponder mice for antigen specific helper T cells. These approaches will allow us to synthesize new insights from the overlap of genetics and immunology to better understand regulation in the immune responses.